Particle sensor device

Abstract

Particle sensor device with: an optical emitting device (50a) which is designed to emit optical radiation (52) within an emission spectrum of the optical emitting device (50a) such that a volume (54) external to or internal to the device containing at least one particle (56) that may be present therein can be at least partially illuminated by the emitted optical radiation (52); an optical detector device (50b) with at least one detection surface (64), wherein the at least one detection surface (64) is arranged such that at least a part of the optical radiation (62) emitted by the optical emitting device (50a) and at least partially scattered by the at least one particle (56) hits the at least one detection surface (64), and wherein the optical detector device (50b) is designed to output at least one information signal (68) regarding an intensity and / or an intensity distribution of the optical radiation (62) incident on the at least one detection surface (64); an evaluation device (70) by means of which, taking into account the at least one information signal (68), information (72) regarding the presence of particles (56), a number of particles, a particle density and / or at least one property of particles (56) can be determined and output; and at least one lens element (58) which is arranged such that the emitted optical radiation (52) can be focused by means of the at least one lens element (58) onto a focus area (60) within the volume (54); characterized by the fact that the optical emitting device (50a) comprises at least one VCSEL laser and / or VeCSEL laser (50a); and the optical detector device (50b) comprises at least one photodiode integrated into a layer structure of the VCSEL laser or VeCSEL laser (50a).

Description

[0001] The invention relates to a particle sensor device. State of the art

[0002] Fig. Figure 1 shows a conventional scattered light particle counter, the components of which are included, for example, in the scattered light particle counter described in DE 10 2013 202 423 A1.

[0003] The in Fig. A schematically represented scattered light particle counter has a laser light source 10, a photodetector 12, and a measuring cell 14 through which an airflow 16 is drawn. A laser beam 18 emitted by the laser light source 10 irradiates a section of the measuring cell 14. If the laser beam 18 encounters at least one particle 16a of the airflow 16 within the irradiated section of the measuring cell 14, at least some photons of the laser beam 18 are scattered as scattering 20 onto the photodetector 12. (The unscratched portion of the laser beam 18 strikes an absorber 22). By using such a conventional scattered light particle counter, information regarding the particles 16a that may be present in the airflow 16 can be determined based on the scattering 20 detected by the photodetector 12.

[0004] Additionally, US 2006 / 0132770A1 describes an optical particle detection system comprising an optical emitter for emitting optical radiation into a volume containing at least one particle that may be present therein, an optical detector with at least one detection surface onto which at least a portion of the optical radiation scattered by the at least one particle strikes, an evaluation device for evaluating at least one output signal from the optical detector to determine information regarding the presence of particles, and at least one lens element for focusing the emitted optical radiation onto a focus area within the volume. Disclosure of the invention

[0005] The invention provides a particle sensor device with the features of claim 1. Advantages of the invention

[0006] The particle sensor device according to the invention, due to the focusing of the emitted optical radiation onto the focus area, enables a sufficiently high intensity of the optical radiation in the focus area, even when using an optical emitter with low emission. This also results in a high intensity of the optical radiation scattered by the at least one particle in the focus area. In particular, the sufficiently high intensity of the optical radiation scattered by the particles in the focus area is ensured even with a small particle size, although the intensity of the scattered optical radiation depends on the particle size of the scattering particles. This also ensures that the optical detector device has high sensitivity. The particle sensor device according to the invention thus enables a precise and (virtually) error-free determination of the output information.

[0007] The particle sensor device according to the invention also exhibits reduced power consumption during operation compared to conventional scattered light particle counters. This facilitates the supply of energy to the particle sensor device for its operation, for example by means of a battery.

[0008] As explained in more detail below, the particle sensor device according to the invention can also be manufactured cost-effectively with a smaller size compared to conventional scattered light particle counters. The particle sensor device according to the invention is therefore also advantageously suited for mobile use or as a sensor for a networked system.

[0009] In an advantageous embodiment of the particle sensor device, at least a portion of the optical radiation focused on the focus area and at least partially scattered by the at least one particle in the focus area is focused onto the at least one detection surface by means of the at least one lens element. This multifunctionality of the at least one lens element allows for the elimination of further optical components in the particle sensor device.

[0010] For example, the emitted optical radiation can be focused by means of the at least one lens element onto a focal area with a focal length of less than 20 cm and / or a focal diameter of less than 1000 µm. In particular, the emitted optical radiation can be focused by means of the at least one lens element onto a focal area with a focal length between 1 and 3 cm and / or a focal diameter between 1 and 20 µm.

[0011] In a further advantageous embodiment of the particle sensor device, the evaluation unit is designed to determine an average particle size, a particle size distribution, an average particle mass, a particle mass distribution, an average particle shape, a particle shape distribution, an average particle velocity, and / or a particle velocity distribution as at least one property of the particles. This makes the particle sensor device highly versatile.

[0012] In a further preferred embodiment of the particle sensor device, the emitted optical radiation and / or the scattered optical radiation are analyzed using the self-mixing interference effect. This can also be described as using the self-mixing interference effect to detect light scattered by the particle, which can be detected, for example, by means of an integrated photodiode. Such an optical detector device enables the automatic filtering out of unwanted ambient light signals. Thus, parasitic light incidence into the external or internal volume of the device impairs the functionality of the particle sensor device less than with a conventional scattered light particle counter.While a reliable darkening of the measuring cell is a basic requirement for the operation of a conventional scattered light particle counter, the particle sensor device described here features an automatic "filtering out" of background signals.

[0013] In an advantageous further development, the particle sensor device additionally includes a mirror assembly by means of which the focus area can be moved one- or two-dimensionally within the volume. A sample volume to be examined for particles can thus be scanned by the focus area.

[0014] In all embodiments described here, the particle sensor device can be a particle detection device and / or a particle counter device. Brief description of the drawings

[0015] Further features and advantages of the present invention are explained below with reference to the figures. They show: Fig. 1 a conventional scattered light particle counter; Fig. 2a and Fig. 2b a schematic representation of a first embodiment of the particle sensor device and a Fourier spectrum to explain its operation; and Fig. 3 a schematic representation of a second embodiment of the particle sensor device. Embodiments of the invention

[0016] Fig. 2a and Fig. Figure 2b shows a schematic representation of a first embodiment of the particle sensor device and a Fourier spectrum to explain its operation.

[0017] The in Fig. Figure 2a, a schematically depicted particle sensor device, has an optical emitter 50a designed to emit optical radiation 52 within an emission spectrum of the optical emitter 50a. The emission spectrum of the optical emitter 50a can, for example, lie in a wavelength range from 350 nm to 1150 nm, particularly in the visible wavelength range. However, it is expressly pointed out that the emission spectrum of the optical emitter 50a is not limited to this wavelength range, and in particular not to the visible wavelength range. Thus, at least part of the emission spectrum of the optical emitter 50a can also lie in the infrared and / or UV range. In particular, the optical emitter 50a can also be designed to emit monochromatic optical radiation 52.Likewise, the optical emitting device 50a can be designed to emit polychromatic optical radiation 52.

[0018] The optical emitting device 50a can, in particular, comprise a laser 50a. If pulsed optical radiation 52 is preferred for the particle sensor device, the optical emitting device 50a can also be a pulsed laser 50a. Furthermore, a laser 50a used for the optical emitting device 50a can emit a laser beam with a (virtually) arbitrary beam diameter as optical radiation 52. The suitability of a laser 50a for the optical emitting device 50a is therefore (virtually) not a prerequisite for the laser beam emitted as optical radiation 52.

[0019] In one embodiment of the invention, the optical emitting device 50a comprises a VCSEL laser 50a (Vertical-Cavity Surface-Emitting Laser). Such a VCSEL laser 50a, which is also frequently referred to as a surface emitter 50a, is generally a semiconductor laser in which the optical radiation 52 is emitted perpendicular to a functionalized semiconductor chip plane. The use of the VCSEL laser 50a for the optical emitting device 50a improves the miniaturization of the particle sensor device.

[0020] The in Fig. 2a The particle sensor device shown schematically can be used to detect or investigate particles 56 that may be present in at least a portion of a volume 54. The respective volume 54 can be an internal volume 54 of the device, such as a sample chamber / measuring chamber of the particle sensor device. However, the particle sensor device can also be designed to detect or investigate particles 56 in at least a portion of the external volume 54. In this case, the particle sensor device is preferably arranged on the external volume 54 such that the functions of its components described below can be performed.

[0021] The volume 54 (containing at least one particle 56 that may be present therein) can in all cases be at least partially illuminated by the optical radiation 52 emitted by the optical emitting device 50a. Furthermore, the particle sensor device has at least one lens element / focusing element 58, which is arranged such that the optical radiation 52 emitted (by the optical emitting device 50a) can be focused / is focused by means of the at least one lens element / focusing element 58 onto a focus area 60 within the volume 54.Preferably, the optical radiation 52 emitted (by the optical emitting device 50a) can be focused onto the focus area 60 within the volume 54 by means of the at least one lens element / focusing element 58 such that only within the focus area 60 there is a high intensity of the emitted optical radiation 52, while at the same time a residual area of ​​the volume 54 outside the focus area 60 has a significantly lower intensity of the emitted optical radiation 52.

[0022] A preferred focal point / focus area 60 should have a diameter of less than 1000 µm. In particular, a diameter of 1 to 20 µm is advantageous. In this way, even with a low intensity of the optical radiation 52 emitted (by the optical emitter 50a), it can be ensured that an increased intensity of the emitted optical radiation 52 is present within the focus area 60. Even with a comparatively weak emission from the optical emitter 50a, the intensity of the optical radiation 52 emitted (by the optical emitter 50a) is thus sufficiently high to guarantee an optically easily detectable scattering 62 on the at least one particle 56 present in the focus area 60.The ease of detection of the scattering 62 caused by the at least one particle 56 present in the focus area 60 also improves the accuracy of results when investigating the possible presence of particles 56 and / or when determining their properties.

[0023] This enables the detection and / or investigation of particles 56 (almost) independently of any material present in the volume 54, such as a gas and / or a liquid. Therefore, the applicability of the particle sensor device is hardly limited to the material (possibly containing particles 56). This increases the applicability of the particle sensor device.

[0024] The term "at least one lens element / focusing element 58" can refer to any optical element suitable for focusing light. For example, the at least one lens element / focusing element 58 can be a single focusing lens 58. Thus, a cost-effective component can be used as the at least one lens element / focusing element 58 in the particle sensor device. A preferred focus length is less than 20 cm; in particular, 1–3 cm is advantageous.

[0025] The particle sensor device also has an optical detector 50b with at least one detection surface 64. The at least one detection surface 64 is arranged such that at least a portion of the optical radiation emitted by the optical emitter 50a and at least partially scattered by the at least one particle 56 (in the focus area 60) strikes the at least one detection surface 64 (as scattering 62). Due to the focusing of the optical radiation 52 (emitted by the optical emitter 50a) onto the focus area 60 and the resulting high intensity of the optical radiation 52 in the focus area 60, it is ensured that even with a small number of particles 56 in the focus area 60 and / or a small particle size in the focus area 60, scattering 62 with an easily and reliably detectable intensity still strikes the at least one detection surface 64.This can also be described as follows: due to the strong focusing, a narrowly specified distance range is defined as the focus range 60, within which a sufficiently high intensity of scattering 62 can be reliably generated to ensure a significant scattering signal even with a small number of particles 64 and / or a small particle size in the focus range 60. This creates a high and reliable sensitivity of the particle sensor device, even to a few particles 56 with a small particle size.

[0026] The comparatively high intensity of the scattering 62 (even with a small number of particles 64 and / or a small particle size in the focus area 60) also allows for a cost-effective and space-saving design of the optical detector device 50b. Thus, cost-effective detectors / photodiodes requiring little installation space can be used for the optical detector device 50b on the particle sensor device.

[0027] The optical emitter 50a and the optical detector 50b need not be understood as separate devices. Instead, the optical emitter 50a and the optical detector 50b can be configured as a single optical emitter and detector 50a and 50b. For example, the optical emitter 50a and the optical detector 50b can also be configured on and / or in a common chip 66.

[0028] If the optical emitter 50a comprises at least one VCSEL and / or VeCSEL laser 50a, the optical detector 50b includes at least one photodiode integrated into a layer structure of the VCSEL or VeCSEL laser 50a. Such an optical emitter and detector 50a and 50b, or the corresponding chip 66, can be referred to as an SMI VCSEL sensor 66 (integrated self-mixing VCSEL sensor 66). In such a VCSEL sensor 66, the detection of the scattering 62 incident on the at least one detection surface 64 is carried out by means of interference of the emission with the incident scattering 62. Therefore, in the VCSEL sensor 66, light incident on the at least one detection surface 64 that is not attributable to the scattering 62 (at the at least one particle 56 present in the focus area 60) is automatically filtered out.This also eliminates the conventional need to shield volume 54 from ambient light for the detection or examination of particles 56. The costs and space requirements for light shielding devices are thus eliminated in the particle sensor device.

[0029] When the devices 50a and 50b are integrated into the chip 66, at least a portion of the optical radiation / scattering 62, which is focused on the focus area 60 and at least partially scattered by the at least one particle 56 in the focus area 60, can be focused back onto the at least one detection surface 64 by means of the at least one lens element / focusing element 58. This multifunctionality of the at least one lens element / focusing element 58, such as the (single) focusing lens 58, allows for the elimination of further optical components in the particle sensor device. Furthermore, this ensures that (almost) exclusively the scattering 62 from the focus area 60 strikes the at least one detection surface 64.The at least one lens element / focusing element 58, in particular the (single) focusing lens 58, thus also achieves a further "spatially resolved filtering out" of unwanted scattered radiation from the remaining area of ​​the volume 54 (outside the focus area 60). This improves the detection accuracy of the particle sensor device and reduces its error rate.

[0030] However, the trainability of the particle sensor device is not limited to the joint integration of the devices 50a and 50b into the chip 66 or on a specific chip type of the common chip 66.

[0031] The optical detector device 50b is designed to output at least one information signal / sensor signal 68 regarding the intensity and / or intensity distribution of the optical radiation / scattering 62 incident on the at least one detection surface 64. The particle sensor device also has an evaluation unit 70 by means of which, taking into account the at least one information signal / sensor signal 68, information 72 regarding the presence of particles 56, a particle number, a particle density and / or a property of particles 56 can be determined and output.For example, the evaluation device 70 can be designed to determine a mean particle size, a particle size distribution, a mean particle mass, a particle mass distribution, a mean particle shape, a particle shape distribution, a mean particle velocity and / or a particle velocity distribution as at least one property of particles 56.

[0032] Fig. Figure 2b shows a coordinate system whose abscissa represents a frequency f (in Hertz) and whose ordinate represents an intensity I for an SMI VCSEL sensor. A Fourier spectrum / Fourier transform of an intensity distribution is shown as an example of a possible information signal / sensor signal 68 of the optical detector device 50b. Based on the frequency bands present, the presence of particles 56 and their velocities can be detected / measured. (The average particle size of the particles 56 used for this experiment was 3 µm.) It can be seen that individual particles can also be detected using the particle sensor device. Fig. However, 2b is only to be interpreted as an example.

[0033] The further training offered by the [profession] is advantageous. Fig. Figure 2a schematically depicts a particle sensor device and additionally includes a (merely schematically depicted) mirror arrangement 74, by means of which the focus area 60 can be displaced one- or two-dimensionally within the volume 64. The mirror arrangement 74 can, for example, comprise a single mirror that is adjustable about one or two axes of oscillation. Likewise, the mirror arrangement 74 can also comprise two mirrors adjustable about one axis of oscillation, wherein the two axes of oscillation of the different mirrors are inclined, preferably perpendicular, to each other. The at least one mirror of the mirror arrangement 74 can, for example, be a MEMS mirror. The adjustment range of the at least one mirror of the mirror arrangement 74 is preferably less than 45°, in particular less than 20°. However, the adjustment range of the at least one mirror of the mirror arrangement 74 can be up to 360°.

[0034] Equipping the particle sensor device with the mirror assembly 74 enables the scanning of a comparatively large area of ​​the volume 54, in particular the entire volume 54, even though the focus area 60 currently being examined (within a short time interval) remains small. Therefore, it is no longer necessary to actively guide particles 56 (e.g., by means of an air or liquid flow) into the focus area 60. Suction and / or pumping devices can thus be eliminated from the particle sensor device.

[0035] Fig. Figure 3 shows a schematic representation of a second embodiment of the particle sensor device.

[0036] The in Fig.The particle sensor device shown schematically also has optics which focus the emitted optical radiation 52 onto a focal area 60 (in the middle of a beam path). This results in increased luminance in the focal area 60 and an increased intensity of scattering 62 from the focal area 60.

[0037] In this case as well, the scattering 62 is generated by the at least one particle 56 in the focus area 60 and directed via the optics back onto a common chip 66 of the devices 50a and 50b. Only particles 56 that are in (or near) the focus area 60 generate scattering falling onto the at least one detection surface 64, while the unwanted scattered radiation from a residual area of ​​the volume 54 (outside the focus area 60) can be filtered out (spatially and spectrally).

[0038] It can be seen that the focus area 60 can be moved in at least one spatial direction 76 by means of the mirror device 74 such that a two-dimensional fan-shaped or a three-dimensional funnel-shaped area of ​​the volume 54 can be scanned. By scanning the focus area 60 in this way, an enlarged area can be examined for the presence of particles 56 or for their properties. This makes it possible, for example, to significantly reduce the measurement time for obtaining a statistically relevant average value of the particle density per unit volume.

[0039] All embodiments of the particle sensor device described above can be used as particle detection devices and / or particle counters. They enable the emitted radiation 52 to be focused such that only the scattering 62 of particles 56 located in the focus area 60 at approximately ± 20% of the focal length is detected by at least one detection surface 64.

[0040] In all the embodiments described above, the emitted optical radiation 52 can be focused by means of the at least one lens element / focusing element 58 onto a focus area 60 with a focus length of less than 20 cm and / or a focus diameter of less than 1000 µm. In particular, the focus length can be less than 5 cm. Preferably, the focus length is between 1 and 3 cm. The focus diameter can be less than 100 µm, preferably between 1 and 20 µm.

[0041] All particle sensor devices described above can have a compact design. In particular, each particle sensor device can require less than 1 cm² of installation space. 3 Furthermore, each of the particle sensor devices described above can be manufactured cost-effectively.

Claims

[1] Particle sensor device with: an optical emitting device (50a) which is designed to emit optical radiation (52) within an emission spectrum of the optical emitting device (50a) such that a volume (54) external to or internal to the device containing at least one particle (56) that may be present therein can be at least partially illuminated by the emitted optical radiation (52); an optical detector device (50b) with at least one detection surface (64), wherein the at least one detection surface (64) is arranged such that at least a part of the optical radiation (62) emitted by the optical emitting device (50a) and at least partially scattered by the at least one particle (56) hits the at least one detection surface (64), and wherein the optical detector device (50b) is designed to output at least one information signal (68) regarding an intensity and / or an intensity distribution of the optical radiation (62) incident on the at least one detection surface (64); an evaluation device (70) by means of which, taking into account the at least one information signal (68), information (72) regarding the presence of particles (56), a number of particles, a particle density and / or at least one property of particles (56) can be determined and output; and at least one lens element (58) which is arranged such that the emitted optical radiation (52) can be focused by means of the at least one lens element (58) onto a focus area (60) within the volume (54); characterized by , that the optical emitting device (50a) comprises at least one VCSEL laser and / or VeCSEL laser (50a); and the optical detector device (50b) comprises at least one photodiode integrated into a layer structure of the VCSEL laser or VeCSEL laser (50a). [2] Particle sensor device according to claim 1, wherein at least a part of the optical radiation (62) focused on the focus area (60) and at least partially scattered on the at least one particle (56) in the focus area (60) can be focused onto the at least one detection surface (64) by means of the at least one lens element (58). [3] Particle sensor device according to claim 1 or 2, wherein the emitted optical radiation (52) can be focused by means of the at least one lens element (58) onto a focus area (60) with a focus length of less than 20 cm and / or a focus diameter of less than 1000 µm. [4] Particle sensor device according to claim 3, wherein the emitted optical radiation (52) can be focused by means of the at least one lens element (58) onto a focus area (60) with a focus length between 1 to 3 cm and / or a focus diameter between 1 to 20 µm. [5] Particle sensor device according to one of the preceding claims, wherein the evaluation device (70) is designed to determine an average particle size, a particle size distribution, an average particle mass, a particle mass distribution, an average particle shape, a particle shape distribution, an average particle velocity and / or a particle velocity distribution as the at least one property of particles (56). [6] Particle sensor device according to one of the preceding claims, wherein the emitted optical radiation (52) and / or the scattered optical radiation (62) is analyzed by means of the self mixing interference effect. [7] Particle sensor device according to one of the preceding claims, wherein the particle sensor device additionally comprises a mirror device (74) by means of which the focus area (60) can be moved one- or two-dimensionally within the volume (54). [8] Particle sensor device according to one of the preceding claims, wherein the particle sensor device is a particle detection device and / or a particle counter device.

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